Is there some reason to have only -one- guard...
Expense. I'm sure you gasp and say "how can you spare any expense to protect out children?" Assets are finite and must be allocated among a number of things that call for infinite expense to assuage consciences and make people feel good.Loading it all to one end that can be much more cheaply provided by more sure and non statist methods. It is called concealed carry. It only requires that the potential murderer maniac know that he does not know hoe many or, most importantly, which adults on the premises are armed. Perhaps none are but so long as the possibility exists the maniac will not do his thing at that place.